Flakes from multilayer iridescent films for use in paints and coatings

ABSTRACT

Comminuted particles of iridescent laminate film are prepared by supporting the film on a strippable substrate prior to the processing of the film into particulate form.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to flakes from multilayeriridescent films for use in paints and coatings.

[0002] Multilayer plastic films which have alternating layers of twopolymers of different refractive indexes are iridescent when thoseindividual layers are of suitable optical thickness. The iridescentcolor is produced by the phenomenon of light interferences. The pair ofalternating polymers constitute the optical core. Usually, the integraloutermost layers or skin layers are thicker than the layers in theoptical core. This thicker skin may consist of one of the components inthe optical core or may be a different polymer which is utilized toimpart desired permanent physical, mechanical or other properties to thefilm. The multilayer structure is conveniently produced by a coextrusionprocess. Such films are described in Re U.S. Pat. No. 31,780 to Cooper,Shetty and Pinsky, and U.S. Pat. No. 5,089,318 and U.S. Pat. No.5,451,449, both to Shetty and Cooper which are hereby incorporated byreference, and other patents.

[0003] The known laminate iridescent films have been used to prepareflakes which can be used to produce a “sparkle” appearance in a varietyof applications but have not been used in coating compositions such as,for example, automotive clear coat-base coat systems because oflimitations on the particle thickness and size obtainable with suchknown iridescent films. Such size limitations are due to the fact thatthe production of flakes is subject to competing requirements. Theiridescent films need to be brittle so that they can be cut into flakesbut at the same time, they require sufficient physical properties topermit handling on the production machinery which makes the flakes.

[0004] As a practical matter, the iridescent laminate film flakes aremade by cutting the films using precision cutting machinery. Themachines used to precision cut iridescent laminate films are web fed andcan only take widths narrower than 5.5 inches (ca 14 cm). Therefore, theiridescent laminate films have to have sufficient physical properties soas to be able to be made as a wide web on the coextrusion equipment andthen be slit into narrower webs (5.5 inches or narrower) and rewound.These narrow rolls are, subsequently, unwound and fed into the cuttingmachines. To satisfy competing demands, it has been found necessary thatthe films from which the flakes are made have a minimum thickness of 1mil (25.4 microns) and that the shortest edge dimension of the flakesmade be approximately 4 mils (101 microns) or greater.

[0005] It was thought possible to produce particles smaller than 4 mils(101 microns) from films thinner than 1 mil (25.4 microns) through amilling or grinding operation but it was found that the laminate filmproducts currently produced are not sufficiently brittle to be milled orground. Unfortunately, those film formulation which are brittle enoughto be milled or ground cannot be coextruded because the laminate filmbreaks at some point during the web handling and winding process.

[0006] An iridescent laminate film product capable of being size reducedand a process to accomplish this size reduction is therefore stillneeded. The present invention addresses this need.

SUMMARY OF THE INVENTION

[0007] The present invention relates to comminuted particles ofiridescent laminate films and their production. More particularity, itrelates to particles produced by temporarily supporting the laminatefilm on a stripable substrate and thereafter removing the support andcomminuting the laminate film.

[0008] As a result of the invention, it is now possible to make theflakes from laminate films which have a thickness of less that 1 mil(25.4 microns), preferably about 0.25-0.75 mil, and for the flakes madeto have a longest edge dimension of less than approximately 4 mils (101microns), preferably about 0.2-3.8 mils. In those instruments thatmeasure particle size using a spherical model, the longest edgedimension is reported as a diameter and in that case, the diameter willbe less than about 150 microns and preferably about 7 to 135 microns.

DESCRIPTION OF THE INVENTION

[0009] In accordance with the present invention, there is provided asupported thermoplastic resinous multilayer laminate film of a pluralityof very thin layers of substantially uniform thickness, the layers beinggenerally parallel and the contiguous adjacent layers being of differenttransparent thermoplastic resinous materials. The multilayer laminatefilm is supported on a carrier layer and adhered thereto such that thesupport layer can be readily stripped from the film.

[0010] The multilayer laminate film preferably has at least 10 of thevery thin layers, more preferably at least 35 and most preferably atleast 70. The individual layers generally have a thickness of about 30to 500 nm.

[0011] The adjacent layers of the laminate film preferably differ inrefractive index by at least about 0.03 and more preferably by at leastabout 0.06.

[0012] Any transparent thermoplastic resinous materials can be used inthe present invention. The preferred transparent thermoplastic resinousmaterials of the laminate film are polyethylene terephthalate (PET),polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), glycolmodified polyethylene terephthalate (PETG) and polystyrene (PS).Combinations which can be employed include PMMA/PBT, PMMA/PET andPMMA/PS.

[0013] One of the advantages of the present invention is thatcombinations which would otherwise be too brittle to be handledconveniently can now be easily employed. Some film formulations are notbrittle but elongate when cutting is attempted, thereby making itdifficult or impossible to comminute into flakes. Another advantage ofthe invention is that it allows laminate film formulations which havevery low elongation to be size reduced to the desired particle sizes byprecision cutting or possibly by milling.

[0014] The carrier can be any material which is weakly adherent to theiridescent laminate film such as, for instance, a polymer support,metallic support, and the like. The carrier is applied in any convenientthickness on one surface of the multilayer laminate film to permit it tobe produced in wide lengths, trimmed and slit into narrow lengths (whenprecision cutting is contemplated) and wound into rolls. Application canbe by coextrusion with the iridescent laminate film or the laminate filmcan be extruded onto a solid carrier web or by any other convenientmeans. The only requirement is that the carrier not have an adverseeffect on the multilayer laminate film and be weakly adherent to theiridescent laminate film. By weakly adherent is meant that the supportlayer can be readily stripped from the laminate film at an appropriatetime, e.g. on a slitter/rewinder.

[0015] The carrier is preferably a polymer and the polymer is preferablya polyolefin, which may be thermoplastic and may be transparent oropaque. The polyolefin is preferably coextrudable with the laminatefilm, an attribute which facilitates the production process. Typicalpolyolefins include high density polyethylene, low density polyethylene,LLDPE, polypropylene, and the like. Polymers other than polyolefins,such as polyesters, can also be used.

[0016] The following examples are illustrative:

EXAMPLE 1

[0017] Polyethylene terephthalate (PET) thermoplastic polyester was fedto the feedblock from one extruder and polymethyl methacrylate (PMMA)from a second extruder to form a 115 layer optical core, and a layer(about 20% of the total thickness) of polyethylene was added to onesurface by means of a third extruder to form a 0.73 mil (18.5 micron)thick laminate iridescent film. The laminate film after stripping thepolyethylene layer was brightly iridescent and was prevailing red andgreen when seen by reflection at perpendicular incidence, and blue andpink when seen by transmission at perpendicular incidence.

[0018] The supported multilayer laminates iridescent film was comminutedas follows. First, the carrier web and the iridescent laminate film wereseparated from one another. The separated film was then cut into flakesin a Granulator and then milled with cooling. The flakes could be usedin any application where a “sparkle” appearance was desired. Forinstance, they can be incorporated into either or both of the clear coatand base coat of an automotive coating system and either of thesecoatings has have additional colorants therein.

EXAMPLE 2

[0019] A multilayer laminate structure with the same polymers in theoptical core as in

EXAMPLE 1 is prepared and flaked as there described except that theoptical core had 99 layers. EXAMPLES 3-7

[0020] The procedure of EXAMPLE 1 was repeated with the followingmaterials: Total No. of High Index Low Index Support Layer ExampleLayers Polymer Polymer Polymer 3 116 PET PMMA Polypropylene 4 116 PSPMMA Polyethylene 5 116 PBT PMMA LLDPE 6 116 PETG PMMA Polypropylene 7116 PET PMMA Polyethylene

[0021] Various changes and modifications can be made in the presentinvention without departing from the spirit and scope thereof. Thevarious embodiments which have been described herein were forillustration purposes only and were not intended to be limiting on thepresent invention.

What is claimed is:
 1. A transparent thermoplastic iridescent laminatefilm of at least 10 very thin layers of substantially uniform thickness,said layers being generally parallel, the contiguous adjacent layersbeing of different transparent thermoplastic resinous materials whoseindex of refraction differs by at least about 0.03 releasably bonded toa supporting substrate.
 2. The supported iridescent laminate filmaccording to claim 1 , wherein said laminate film is less than 1 mil inthickness.
 3. The supported iridescent laminate film according to claim1 , wherein said laminate film is about 0.25 to 0.75 mils in thickness.4. The supported iridescent laminate film according to claim 1 , whereinsaid support is a polyolefin.
 5. The supported iridescent laminate filmaccording to claim 4 , wherein said laminate film is less than 1 mil inthickness.
 6. The supported iridescent laminate film according to claim5 , wherein said laminate film is about 0.25 to 0.75 mils in thickness.7. The supported iridescent laminate film according to claim 6 , whereinat least one of said resinous materials is selected from the groupconsisting of polyethylene terephthalate, polymethyl methacrylate,polybutylene terephthalate, glycol modified polyethylene terephthalateand polystyrene, and wherein the contiguous adjacent layers of differenttransparent thermoplastic resinous materials have an index of refractiondiffers by at least about 0.06.
 8. The supported iridescent laminatefilm according to claim 4 , wherein one of said resinous materials ispolymethyl methacrylate and the other resinous material is selected fromthe group consisting of polyethylene terephthalate, polybutyleneterephthalate, and polystyrene.
 9. The supported iridescent laminatefilm according to claim 1 , wherein one of said resinous materials ispolymethyl methacrylate and the other resinous material is selected fromthe group consisting of polyethylene terephthalate, polybutyleneterephthalate, and polystyrene.
 10. A process for producing iridescentlaminate films suitable for comminution comprising forming a transparentthermoplastic laminate film of at least 10 very thin layers ofsubstantially uniform thickness, said layers being generally parallel,the contiguous adjacent layers being of different transparentthermoplastic resinous materials whose index of refraction differs by atleast about 0.03 and releasably bonded said film to a supportingsubstrate.
 11. The process of claim 10 , wherein said supportingsubstrate is a polyolefin.
 12. The process of claim 11 , comprisingforming said supported laminate film by coextrusion.
 13. The process ofclaim 10 , further comprising separating said supporting substrate andsaid laminate film; and comminuting said laminate film.
 14. The processof claim 10 , wherein said laminate film is less than 1 mil in thicknessand wherein said supporting substrate is a polyolefin.
 15. The processof claim 14 , wherein said comminuting said laminate film is such thatthe largest edge dimension of the comminuted particles is less thanabout 4 mils.
 16. The process of claim 13 , wherein said supportedlaminate film is cut to a width of not greater than about 5.5 inchesprior to said separating step.
 17. The process of claim 13 , wherein atleast one of said resinous materials is selected from the groupconsisting of polyethylene terephthalate, polymethyl methacrylate,polybutylene terephthalate, glycol modified polyethylene terephthalateand polystyrene, and wherein the contiguous adjacent layers of differenttransparent thermoplastic resinous materials have an index of refractiondiffers by at least about 0.06.
 18. The process of claim 13 , whereinone of said resinous materials is polymethyl methacrylate and the otherresinous material is selected from the group consisting of polyethyleneterephthalate, polybutylene terephthalate, and polystyrene.
 19. Aplurality of particles each of which comprises a transparentthermoplastic laminate film of at least 10 very thin layers ofsubstantially uniform thickness, said layers being generally parallel,the contiguous adjacent layers being of different transparentthermoplastic resinous materials whose index of refraction differs by atleast about 0.03, the largest edge dimension of the particle being lessthan about 4 mils and the thickness being less that about 1 mil.
 20. Theplurality of particles of claim 19 , wherein said laminate film of theparticle is about 0.25 to 0.75 mils in thickness.
 21. The plurality ofparticles of claim 20 , wherein the largest edge dimension of saidlaminate film particle is about 0.2 to 3.8 mils.
 22. The plurality ofparticles of claim 21 , wherein one of said resinous materials ispolymethyl methacrylate and the other resinous material is selected fromthe group consisting of polyethylene terephthalate, polybutyleneterephthalate, and polystyrene.
 23. The plurality of particles of claim19 , wherein at least one of said resinous materials is selected fromthe group consisting of polyethylene terephthalate, polymethylmethacrylate, polybutylene terephthalate, glycol modified polyethyleneterephthalate and polystyrene, and wherein the contiguous adjacentlayers of different transparent thermoplastic resinous materials have anindex of refraction differs by at least about 0.06.